Dr. Henry Pym first appeared in Tales to Astonish #27, in a story by Larry Lieber–the younger brother of Stan Lee–and Jack Kirby. The tale was called, “The Man in the Ant Hill.” In that appearance, he was just a dude in a lab coat who shrunk himself to ant size. But Stan Lee was sold on the concept, and in issue #38 he became Ant Man, and his stories were the regular feature in Tales to Astonish. Soon after, Janet Van Dyne came on the scene and became Wasp, and then the duo formed The Avengers.
He would go on to have multiple identities and be a founding member of The Avengers.
The book hit the stands on September 28, 1961.